Marital status and risk of dementia: a nationwide population-based prospective study from Sweden.

Objectives: To examine the association between marital status and dementia in a cohort of young-old (50-64) and middle-old (65-74) adults, and also whether this may differ by gender.

Design: Prospective population-based study with follow-up time of up to 10 years.

Setting: Swedish national register-based study.

Participants: 2,288,489 individuals, aged 50-74 years, without prior dementia diagnosis at baseline. Dementia was identified using the Swedish National Patient Register and the Cause of Death Register.

Outcome Measures: The influence of marital status on dementia was analysed using Cox proportional hazards models, adjusted stepwise for multiple covariates (model 1: adjusted for age and gender; and model 2: additionally adjusted for having adult children, education, income and prior cardiovascular disease).

Results: During follow-up, 31,572 individuals in the study were identified as demented. Cox regression showed each non-married subcategory to be associated with a significantly higher risk of dementia than the married group, with the highest risk observed among people in the young-old age group, especially among those who were divorced or single (HRs 1.79 vs 1.71, fully adjusted model). Analyses stratified by gender showed gender differences in the young-old group, with indications of divorced men having a higher relative risk compared with divorced women (HRs 2.1 vs 1.7, only-age adjusted model). However, in the fully adjusted model, these differences were attenuated and there was no longer any significant difference between male and female participants.

Conclusions: Our results suggest that those living alone as non-marrieds may be at risk for early-onset and late-onset dementia. Although more research is needed to understand the underlying mechanism by which marital status is associated with dementia, this suggests that social relationships should be taken seriously as a risk factor for dementia and that social-based interventions may provide an opportunity to reduce the overall dementia risk.